The present invention relates to a method for producing a pattern film-coated article, particularly, a method for producing a pattern film-coated article which comprises the steps of coating a photosensitive composition containing an organometallic compound having photosensitivity on a substrate, irradiating the coated composition with light to polymerize and cure the coated film and removing unexposed portions, and to a photosensitive composition.
The development of a photosensitive material for forming a pattern film has heretofore been under way, and a number of proposals associated with such a material have been made. In general, the properties required for the photosensitive material are, for example, (1) having high sensitivity to irradiated energy, (2) having high resolution, that is, having excellent pattern accuracy and processability and (3) having high adhesion to a substrate. It has heretofore been attempted to form a thin-film pattern of an oxide of a metal element and an amphoteric element by using a sol-gel material having photosensitivity.
The production of an optical waveguide element having a grating by exposure and development (leaching) using a photosensitive material comprising methacryloxypropyltrimethoxysilane, zirconium alkoxide and acrylic acid is described in JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 16, No. 9, pp. 1,640 to 1,646, SEPTEMBER, 1998, SPIE Vol. 3,282, pp. 17 to 30, and SPIE Vol. 3,282, pp. 50 to 58.
In the case of the above method, however, it is difficult to fully remove unexposed portions of the film during development after exposure, so that a good pattern cannot be obtained. Therefore, there are such problems that a waveguide laser beam leaks in the production of a waveguide and that a distinct pattern of diffracted lights cannot be obtained and the diffracted light beams are blurred or merged in the production of a diffraction grating.
It is therefore the object of the present invention to provide a method for producing a pattern film-coated article which has excellent film formability, can remove unexposed portions of a film completely in the development step after exposing the film to light (or has so-called xe2x80x9cgood leachingxe2x80x9d) and has excellent pattern accuracy; and a photosensitive composition for producing the article.
According to the present invention, firstly, the above object and advantage of the present invention can be achieved by a method for producing a pattern film-coated article which comprises the steps of coating a photosensitive composition containing an organometallic or organosilicon compound having photosensitivity and a hydrolyzable metal or silicon alkoxide on a substrate, irradiating the coated film on the substrate with light to polymerize the exposed portions of the coated film and then dissolving its unexposed portions of the coated film to remove them, wherein the above organometallic or organosilicon compound is an allyl group-containing metal or silicon alkoxide.
According to the present invention, secondly, the above object and advantage of the present invention can be achieved by a method for producing a pattern film-coated article which comprises the steps of coating a photosensitive composition containing an allyl group-containing trialkoxysilane on a substrate, irradiating the coated film on the substrate with light to polymerize the exposed portions of the coated film and then dissolving its unexposed portions of the coated film to remove them.
According to the present invention, thirdly, the above object and advantage of the present invention can be achieved by a photosensitive composition comprising an allyl group-containing metal or silicon alkoxide, a photoreaction initiator, a polymerization promoter and water as main components.
Illustrative examples of the allyl group-containing metal or silicon alkoxide which has photosensitivity and which is used in the photosensitive composition of the present invention include an allyl group-containing silicon alkoxide, an allyl group-containing titanium alkoxide, an allyl group-containing zirconium alkoxide and an allyl group-containing aluminum alkoxide. Of these, the allyl group-containing silicon alkoxide is preferably used. As the allyl group-containing silicon alkoxide (to be sometimes referred to simply as xe2x80x9callylsilanexe2x80x9dhereinafter), allyl group-containing trialkoxysilanes such as allyltrimethoxysilane and allyltriethoxysilane; diallyldialkoxysilanes such as diallyldimethoxysilane and diallyldiethoxysilane; allylaminotrimethoxysilane; and chloroallylsilanes such as allyltrichlorosilane and diallyldichlorosilane are used. Of these, allyltrimethoxysilane and allyltriethoxysilane are particularly preferably used. Attention must be paid to the working environment under which chloroallylsilanes are used since they produce a hydrogen chloride gas at the time of reaction.
The content of the above allyl group-containing metal or silicon alkoxide having photosensitivity in the above photosensitive composition is preferably 5 to 95.49% by weight.
Illustrative examples of the hydrolyzable metal or silicon alkoxide used in the photosensitive composition of the present invention include a silicon alkoxide, a titanium alkoxide, a zirconium alkoxide and an aluminum alkoxide. Of these, a silicon tetra- or tri-alkoxide, a titanium tetra- or tri-alkoxide, a zirconium tetra- or tri-alkoxide, and an aluminum trialkoxide are preferably used. Illustrative examples of the above tetraalkoxides and aluminum trialkoxide include tetraethoxysilane, tetramethoxysilane, tributoxyaluminum, tetrapropoxyzirconium, tetrabutoxyzirconium, tetraisopropoxytitanium and tetrabutoxytitanium.
Illustrative examples of the silicon trialkoxide, titanium trialkoxide and zirconium trialkoxide include methyltriethoxysilane, methyltrimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, 3-methacryloxyalkyltrialkoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-(N-allylamino)propyltrimethoxysilane, (2-cyclohexenyl-2-ethyl)trialkoxysilane, 5-(bicycloheptenyl)trialkoxysilane, (acryloxymethyl)phenethyltrialkoxysilane, 1,1-bis(trialkoxysilylmethyl)ethylene, bis(triethoxysilyl)ethylene, bis(triethoxysilyl)-1,7-octanediene, butenyltriethoxysilane, (3-cyclopentadienylpropyl)triethoxysilane, 5-hexenyltrialkoxysilane, O-(methacryloxyethyl)-N-(triethoxysilylpropyl)urethane, 1,7-octadienyltriethoxysilane, 7-octenyltrialkoxysilane, (2,4-pentadienyl)trialkoxysilane, styrylethyltrimethoxysilane, vinyltriisopropenoxysilane; titanium allylacetoacetate triisopropoxide, titanium methacrylate triisopropoxide, titanium methacryloxyethylacetoacetate triisopropoxide, (2-methacryloxyethoxy)triisopropoxytitanate; and zirconium methacryloxyethylacetoacetate triisopropoxide.
Further, an alkoxide of metal and silicon such as di-s-butoxyaluminoxytriethoxysilane and an alkoxide of different types of metals are also used. The hydrolyzable metal or silicon tetraalkoxide may be an oligomer (for example, oligomer having an average degree of polymerization of not higher than 5) and may be partially or wholly hydrolyzed. However, when the content of the hydrolyzable metal or silicon tetraalkoxide is expressed in mol % or wt %, the content of its monomer or the material before hydrolysis is expressed.
These hydrolyzable metal or silicon alkoxides may be chelated by such ligands as xcex2-diketone, e.g., acetylacetone, methylacetylacetone, ethylacetylacetone and diethylacetylacetone, as required. Acetylacetone aluminum and titanium acetylacetonate also serve as a polymerization promoter to be described later.
Of these hydrolyzable metal or silicon alkoxides, tetraethoxysilane, tetramethoxysilane and tetrabutoxy zirconium are particularly preferably used. For example, the hardness of the film can be further increased by using tetrabutoxy zirconium. Further, by using the zirconium alkoxide and/or the titanium alkoxide, the refractive index of the film can be increased to a desired value.
By incorporating the above hydrolyzable metal or silicon alkoxides into the photosensitive composition of the present invention, a film having a strong network can be formed and the chemical resistance and weather resistance of the film can be improved. When the amount of these hydrolyzable metal or silicon alkoxldes is too large, the amount of the above allyl group-containing metal or silicon alkoxides decreases accordingly. Therefore, the amount of the hydrolyzable metal or silicon alkoxides is preferably 1 to 50% by weight, more preferably 5to 40% by weight, in relation to the allylsilanes. The content of the above hydrolyzable metal or silicon alkoxides in the photosensitive composition is preferably 1 to 50% by weight. When an allyltrialkoxysilane such as allyltrimethoxysilane or allyltriethoxysilane is used as the allylsilane in the present invention, the above hydrolyzable metal or silicon alkoxides may not have to be contained in the photosensitive composition. When the hydrolyzable metal or silicon alkoxides are not contained, the content of the above allyl group-containing metal or silicon alkoxides in the above photosensitive composition is preferably not higher than 96.49% by weight. However, when it is desired to further increase the strength, chemical resistance and weather resistance of the film, it is preferable to add the above hydrolyzable metal or silicon alkoxides.
The photosensitive composition in the present invention contains water used for hydrolyzing the above hydrolyzable metal or silicon alkoxides and the above allyl group-containing metal or silicon alkoxides having photosensitivity and, as required, a catalyst which are for promoting the above hydrolysis, a photoreaction initiator, a polymerization promoter and a solvent. The content of water including the water contained in the aqueous solution of the catalyst is 0.8 to 30 times as much as the required stoichiometric ratio and is preferably 1 to 20 times, more preferably 2 to 10 times, as much as the total of the above hydrolyzable metal or silicon alkoxides and the above allyl group-containing metal or silicon alkoxides having photosensitivity in terms of molar ratio. The content of water in the photosensitive composition is preferably 3 to 50% by weight, more preferably 5 to 30% by weight. However, when the above hydrolyzable metal or silicon alkoxides and the above allyl group-containing metal or silicon alkoxides having photosensitivity are already partially or wholly hydrolyzed, the water content may be zero or lower than the above range.
The above catalyst is a component which is preferable to be contained. As the catalyst, inorganic acids such as hydrochloric acid, nitric acid (HNO3) and sulfuric acid and organic acids such as acetic acid, oxalic acid, formic acid, propionic acid and p-toluenesulfonic acid are used. The content of the catalyst varies depending on the type of the acid and the strength (weak acid or strong acid) as a protonic acid. When the content of the catalyst is too low, the hydrolysis and dehydration condensation reaction proceeds slowly, while when it is too high, the condensation reaction proceeds excessively and the molecular weight becomes too large, whereby a precipitate is liable to be formed disadvantageously, or a coating solution is liable to be gelled disadvantageously. Therefore, when hydrochloric acid is used as the acid catalyst, the content of the acid catalyst to be added is preferably 0.01 to 100 millimoles (0.00001 to 0.1 mole), more preferably 0.05 to 50 millimoles per mole of the total of the above hydrolyzable metal or silicon alkoxides and the above allyl group-containing metal or silicon alkoxides having photosensitivity in terms of molar ratio. The content of the acid catalyst in the photosensitive composition is preferably 0.00002 to 10% by weight, more preferably 0.0001 to 1% by weight. However, when the above hydrolyzable metal or silicon alkoxides and the above allyl group-containing metal or silicon alkoxides having photosensitivity are already partially or wholly hydrolyzed, the content of the acid catalyst may be zero or lower than the above range.
The photoreaction initiator used in the photosensitive composition of the present invention is a component which is preferable to be contained and initiates and promotes photopolymerization when the allyl group having a polymerizable carbon-carbon double bond in the above allyl group-containing metal or silicon alkoxide having photosensitivity is irradiated with light. As the initiator, benzophenone, acetophenone, benzoin isopropyl ether, benzoin isobutyl ether, benzoyl peroxide, 1-hydroxycyclohexyl-1-phenylketone (Ciba-GeigyCorporation, xe2x80x9cIrgacure 184xe2x80x9d), 2-hydroxy-2-methyl-1-phenylpropane-1-one (Merck and Co., Inc., xe2x80x9cDalocure 1173xe2x80x9d), 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one (Merck and Co., Inc., xe2x80x9cDalocure 1116xe2x80x9d), 2,2-dimethoxy-2-phenylacetophenone (Ciba-GeigyCorporation, xe2x80x9cIrgacure 651xe2x80x9d) and the like are suitably used. The content of the photoreaction initiator is preferably 0.001 to 0.2 moles per mole of the allyl group-containing metal or silicon alkoxide. Further, the content of the photoreaction initiator in the photosensitive composition is preferably 1 to 20% by weight, more preferably 0.5 to 10% by weight.
The polymerization promoter used in the present invention is a component that is preferable to be contained and serves as a polymerization-promoting catalyst when the above metal or silicon alkoxide and the above allyl group-containing metal or silicon alkoxide are hydrolyzed and then polycondensed to form an Sixe2x80x94Oxe2x80x94Si bond. As the polymerization promoter, organic amines such as triethylamine and n-butylamine; metal acetylacetonatos such as acetylacetone aluminum which is chelated by acetylacetone, titanium acetylacetonato and chromium acetylacetonato; and tin compounds such as octyl tin and stannic chloride are suitably used. The content of the polymerization promoter is preferably 0.0005 to 0.1 moles per mole of the total of the above metal or silicon alkoxide and the above allyl group-containing metal or silicon alkoxide in terms of molar ratio. The content of the polymerization promoter in the photosensitive composition is preferably 0.01 to 10% by weight, more preferably 0.05 to 10% by weight.
An organic solvent which is the solvent used in the present invention is a component that is preferable to be contained. There is a case where the solvent may not have to be intentionally added since an alcohol produced when the above metal or silicon alkoxide and the above allyl group-containing metal or silicon alkoxide are hydrolyzed serves as the solvent. In general, however, a suitable solvent is used according to the type of method for forming the coated film. As the method for forming the coated film, casting, dip coating, gravure coating, flexographic printing, roller coating or the like is suitably used. Of these, the organic solvent used in casting or dip coating is suitably a solvent having a fast evaporation rate. That is, when the evaporation rate of the solvent is too slow, the flowability of the solution becomes high since the coated film is too slow to be dried, whereby a coated film having a uniform thickness may not be obtained. Therefore, alcohol solvents having a fast evaporation rate such as methanol, ethanol, isopropyl alcohol and tert-butoxy alcohol can be suitably used.
On the other hand, the organic solvent used in gravure coating, flexographic printing or roller coating is suitably a solvent having an extremely slow evaporation rate as will be described below. This is because when a solvent having an excessively fast evaporation rate is used, the solvent evaporates before sufficient leveling is done, thereby giving a poor appearance to the coated film. The evaporation rate of the solvent is generally evaluated by a relative evaporation rate index with the evaporation rate of butyl acetate being 100. A solvent having a relative evaporation rate index of not larger than 40 is classified as a solvent having an extremely slow evaporation rate, and such a solvent is preferable as an organic solvent to be used in gravure coating, flexographic printing or roller coating. Illustrative examples of such an organic solvent include ethyl cellosolve, butyl cellosolve, cellosolve acetate, diethylene glycol monoethyl ether, hexylene glycol, diethylene glycol, ethylene glycol, tripropylene glycol, diacetone alcohol and tetrahydrofurfuryl alcohol.
Although it is desirable to use one of the above solvents as the solvent of the coating solution used in the present invention, a mixture of the above solvents may also be used according to the characteristics of the coating method and the coating solution.
The content of the solvent is preferably 0.3 to 5 times, more preferably 0.5 to 3 times as much as the total of the above metal or silicon alkoxide and the above allyl group-containing metal or silicon alkoxide in terms of molar ratio. The content of the solvent in the photosensitive composition is preferably 0 to 50% by weight, more preferably 0 to 20% by weight.
A variety of additives may be added to the photosensitive composition of the present invention. Illustrative examples of such additives include a film thickness-increasing agent which increases the film thickness, viscosity-increasing agent, leveling agent and flow-controlling agent. Specific examples thereof include silicones such as dimethylpolysiloxane and glycols such as polyethylene glycol.
Since the photosensitive composition of the present invention must be eventually irradiated with light to form a pattern, the siloxane polymer must be dissolved in an organic solvent or an alkali aqueous solution from the viewpoint of pattern formability. Therefore, care must be taken on the hydrolysis conditions since leaching becomes difficult to carry out when the degrees of polymerization of the above metal or silicon alkoxide and the above allyl group-containing metal or silicon alkoxide are raised too high. The photosensitive composition comprising the allyl group-containing metal or silicon alkoxide, the hydrolyzable metal or silicon alkoxide, and, as required, the hydrolysis catalyst, the photoreaction initiator, the polymerization promoter, water and the solvent is preferably prepared by mixing these components together and then allowing the mixture to react at room temperature to 50xc2x0 C. for 30 minutes to 12 hours to hydrolyze the mixture.
The photosensitive composition of the present invention preferably contains 5 to 95.49% by weight of the allyl group-containing metal or silicon alkoxide, 1 to 50% by weight of the hydrolyzable metal or silicon alkoxide, 0.5 to 10% by weight of the photoreaction initiator, 0.01 to 10% by weight of the polymerization promoter, 0 to 50% by weight of the solvent and 3 to 50% by weight of water.
Further, the photosensitive composition of the present invention preferably contains 5 to 96.49% by weight of the allyl group-containing trialkoxysilane, 0.5 to 10% by weight of the photoreaction initiator, 0.01 to 10% by weight of the polymerization promoter, 0 to 50% by weight of the solvent and 3 to 50% by weight of water.
The substrate used in the present invention may take any form such as a flat plate, curved plate or stick. The substrate desirably has a small amount of surface warpage (heat distortion length in the direction perpendicular to the surface direction of the substrate per unit length in the surface direction of the substrate). When the amount of warpage is larger than this range, the coated film may be peeled off from the substrate or cracked in the process of forming the film. Therefore, it is preferable to be selective in selecting the material, size and form of the substrate.
Further, this substrate preferably has a linear expansion coefficient of not higher than 5xc3x9710xe2x88x925/xc2x0 C. This is because when the linear expansion coefficient of a substrate made of plastic having a high linear expansion coefficient such as polypropylene (9xc3x9710xe2x88x925 to 15xc3x9710xe2x88x925/xc2x0 C.) is higher than 5xc3x9710xe2x88x925/xc2x0 C., for example, an organopolysiloxane film is peeled off from the substrate or cracked in the process of forming the film. Ordinary inorganic glass has a linear expansion coefficient of not higher than 5xc3x9710xe2x88x925/xc2x0 C. Further, at least the surface of the substrate is preferably comprised of an oxide. This is because when the surface of the substrate which makes contact with the film is not comprised of an oxide, the adhesion strength lowers in the process of forming the film and, in some cases, the film is peeled off from the substrate. Illustrative examples of preferable substrate materials include oxide glass such as silicate glass, borate glass and phosphate glass; quartz, ceramic, metal, silicon, epoxy resins and fibrous glass reinforced polystyrene. A metal cannot be bonded to the film as it is but can be used as the substrate once the surface thereof is treated with an oxide in advance. Of these, float glass (linear expansion coefficient: 1xc3x9710xe2x88x925/xc2x0 C.) is preferable from the viewpoint of cost, and quarts glass (linear expansion coefficient: 8xc3x9710xe2x88x927/xc2x0 C.) and zero expansion glass (linear expansion coefficient: xe2x88x923xc3x9710xe2x88x927 to 0.0xc3x9710xe2x88x927/xc2x0 C., trade name: Neoceram, Zeroduaglass) are the most preferable from the viewpoint of thermal expansion coefficient. Further, when an integrated optical element is to be produced, a silicon substrate (linear expansion coefficient: 41.5xc3x9710xe2x88x927/xc2x0 C.) may be used.
The above photosensitive composition is coated on a substrate having a predetermined shape to a wet thickness of 0.5 to 200 xcexcm to form a coated film, a photomask having a pattern comprising light-transmitting and light-shielding areas having predetermined shapes is placed on the coated film, ultraviolet radiation is irradiated to the coated film via the photomask for 1 seconds to 30 minutes in such a manner that, for example, the light intensity at the irradiated position should be 1 to 200 mW/cm2 to polymerize the exposed portion of the coated film which corresponds to the light-transmitting area of the photomask, the unexposed portion of the coated film which corresponds to the light-shielding area of the photomask is leached (dissolved and removed) by alcohol or an alkali aqueous solution, and the resulting substrate is heated preferably at 80 to 350xc2x0 C. for 10 minutes to 5 hours to cure the coated film, thereby forming an article coated with a pattern film which has a thickness of 100 nm to 50 xcexcm, particularly preferably 100 nm to 10 xcexcm and a shape corresponding to the light-transmitting area pattern of the above photomask, as exemplified by an optical waveguide element, a diffraction grating or other optical element. By the above light irradiation, the photopolymerization (the polymerizable carbon-carbon double bonds of the allyl groups are opened and bonded to others) of the allyl group-containing metal or silicon alkoxides does not occur in the unexposed portion of the coated film, and the allyl group-containing metal or silicon alkoxides are dissolved and removed by solvent together with a hydrolysate of the hydrolyzable metal or silicon alkoxides. The allyl group-containing metal or silicon alkoxides in the exposed portion of the coated film are polymerized by the opening and rebonding of the polymerizable carbon-carbon double bonds contained therein, thereby becoming insoluble to the solvent. Then, by the subsequent heat treatment, the hydrolysis and dehydration condensation reaction of the allyl group-containing metal or silicon alkoxides and hydrolyzable metal or silicon alkoxides in the exposed portion of the coated film is completed and the remaining coated film is cured.
As described above, the photosensitive composition of the present invention is used for the production of a pattern film-coated article in which a portion of a coated film is polymerized and cured by irradiation of light and the unexposed portion of the film is dissolved and removed. In addition, an optical element, such as a microlens, diffraction grating or optical waveguide, or other coated article which has a film having the surface pattern of a shape transferred thereon bonded to a substrate can be produced by placing the photosensitive composition between the substrate and the shape whose surface may take a variety of patterns, pressing them as required, irradiating the whole substrate with light to polymerize and cure the coated photosensitive composition.